Embodiments herein generally relate to implantable medical devices and more particularly, to a leadless cardiac pacemaker with a combined fixation antenna member.
An implantable medical device (IMD) is a medical device that is implanted in a patient to, among other things, monitor electrical activity of a heart, and optionally to deliver therapy, such as a cardiac pacemaker. For cardiac applications, pacemakers are used to deliver pacing pulses to a cardiac chamber to induce a depolarization of that chamber, which is followed by mechanical contraction of that chamber, when a patient's own intrinsic rhythm fails. The IMD further includes sensing circuits that sense electrical activity for the detection of intrinsic cardiac events such as intrinsic atrial depolarizations (detectable as P waves) and intrinsic ventricular depolarizations (detectable as R waves). By monitoring electrical activity, the IMD is able to determine the intrinsic rhythm of the heart and provide stimulation pacing pulses that force atrial and/or ventricular depolarizations at appropriate times in the cardiac cycle to help stabilize the electrical rhythm of the heart.
Some known IMDs utilize one or more electrically-conductive leads that extend from a remotely-located canister or pulse-generator and traverse blood vessels and cardiac chambers to affix connected electrodes to the heart. The housing or canister, referred to as a “can”, has electronics and a power source. The can, including the power and processing circuitry, and a portion of the leads are located outside of the patient's heart, and the power and data signals are relayed to and from the heart via the leads. However, the presence of leads may be associated with and/or cause a number of complications.
To mitigate the limitations and complications associated with transvenous leads and the associated IMD, smaller sized devices configured for intra-cardiac implant without the need for transvenous leads have been proposed. These leadless implantable medical devices (LIMD), such as a leadless cardiac pacemaker, are devoid of leads that pass out of the heart to another component, such as a can located outside of the heart. The entire device is configured to be attached to the heart with a fixation antenna, such as a helical member that screws into endocardial tissue. Thus, the power source and the processing circuitry are contained within the device that is attached to the heart. The LIMD includes electrodes that are affixed directly to the can of the device, instead of being separated by a distance traversed by one or more leads. Each LIMD is capable of local pacing and sensing in the chamber of the heart where it is implanted.
Some IMDs communicate with external devices and/or other implanted devices through a radio frequency (RF) antenna. However, the small size of LIMDs create challenges when designing antenna to satisfy the size limitations to fit within the device. Placing an antenna on the exterior of an LIMD also presents challenges. For example, conventional assembly processes for IMDs do not readily permit the addition of external antenna due to an increase in cost and/or assembly time. In addition, an external antenna on the device can interfere with the fixation antenna's ability to hold the LIMD in place.